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greg |
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/* Copyright (c) 1990 Regents of the University of California */
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#ifndef lint
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static char SCCSid[] = "$SunId$ LBL";
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#endif
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/*
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* Fast malloc for memory hogs and VM environments.
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* Performs a minimum of searching through free lists.
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* bmalloc() doesn't keep track of free lists -- it's basically
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* just a buffered call to sbrk().
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* bfree() puts memory from any source into malloc() free lists.
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* malloc(), realloc() and free() use buckets
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* containing blocks in powers of two, similar to CIT routines.
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*
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* Greg Ward Lawrence Berkeley Laboratory
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*/
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#define NULL 0
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#ifndef ALIGN
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#define ALIGN int /* align type */
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#endif
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#define BYTES_WORD sizeof(ALIGN)
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#ifdef NOVMEM
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#define getpagesize() BYTES_WORD
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#endif
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/* malloc free lists */
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typedef union m_head {
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union m_head *next;
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int bucket;
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ALIGN dummy;
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} M_HEAD;
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#define FIRSTBUCKET 3
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#define NBUCKETS 30
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static M_HEAD *free_list[NBUCKETS];
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char *
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bmalloc(n) /* allocate a block of n bytes, sans header */
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register unsigned n;
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{
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extern char *sbrk();
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static int pagesz = 0;
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static int amnt;
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static char *bpos;
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static int nrem;
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register char *p;
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if (pagesz == 0) { /* initialize */
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amnt = pagesz = getpagesize();
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nrem = (int)sbrk(0); /* page align break */
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nrem = pagesz - (nrem&(pagesz-1));
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bpos = sbrk(nrem); /* word aligned! */
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if ((int)bpos == -1)
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return(NULL);
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}
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n = (n+(BYTES_WORD-1))&~(BYTES_WORD-1); /* word align rqst. */
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if (n > nrem) { /* need more core */
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if (n > amnt) /* increase amount */
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amnt = (n+(pagesz-1))&~(pagesz-1);
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p = sbrk(amnt);
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if ((int)p == -1)
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return(NULL);
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if (p != bpos+nrem) { /* someone called sbrk()! */
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bfree(bpos, nrem);
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bpos = p;
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nrem = amnt;
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} else
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nrem += amnt;
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}
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p = bpos;
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bpos += n; /* advance */
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nrem -= n;
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return(p);
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}
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bfree(p, n) /* free n bytes of random memory */
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char *p;
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unsigned n;
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{
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register M_HEAD *mp;
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register int bucket;
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register unsigned bsiz;
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/* find largest bucket */
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bucket = 0;
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for (bsiz = 1; bsiz+sizeof(M_HEAD) <= n; bsiz <<= 1)
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bucket++;
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mp = (M_HEAD *)p;
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while (bucket > FIRSTBUCKET) {
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bsiz >>= 1;
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bucket--;
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if (n < bsiz+sizeof(M_HEAD)) /* nothing for this bucket */
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continue;
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mp->next = free_list[bucket];
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free_list[bucket] = mp;
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(char *)mp += bsiz+sizeof(M_HEAD);
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n -= bsiz+sizeof(M_HEAD);
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}
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}
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char *
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malloc(n) /* allocate n bytes of memory */
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unsigned n;
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{
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register M_HEAD *mp;
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register int bucket;
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register unsigned bsiz;
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bucket = FIRSTBUCKET;
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for (bsiz = 1<<FIRSTBUCKET; bsiz < n; bsiz <<= 1)
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bucket++;
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if (free_list[bucket] == NULL) {
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mp = (M_HEAD *)bmalloc(bsiz+sizeof(M_HEAD));
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if (mp == NULL)
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return(NULL);
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} else {
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mp = free_list[bucket];
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free_list[bucket] = mp->next;
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}
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mp->bucket = bucket;
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return((char *)(mp+1));
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}
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char *
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realloc(op, n) /* reallocate memory using malloc() */
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char *op;
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unsigned n;
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{
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register char *p;
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register unsigned on;
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if (op != NULL)
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on = 1 << ((M_HEAD *)op-1)->bucket;
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else
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on = 0;
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if (n <= on && n > on>>1)
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return(op); /* same bucket */
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p = malloc(n);
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if (p == NULL)
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return(NULL);
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#ifdef BSD
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bcopy(op, p, n>on ? on : n);
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#else
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(void)memcpy(p, op, n>on ? on : n);
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#endif
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free(op);
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return(p);
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}
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free(p) /* free memory allocated by malloc */
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char *p;
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{
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register M_HEAD *mp;
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register int bucket;
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mp = (M_HEAD *)p - 1;
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bucket = mp->bucket;
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mp->next = free_list[bucket];
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free_list[bucket] = mp;
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}
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#ifndef NOVMEM
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#ifndef BSD
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#include <sys/var.h>
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int
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getpagesize() /* use SYSV var structure to get page size */
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{
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static int pagesz = 0;
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struct var v;
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if (pagesz == 0) {
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uvar(&v);
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pagesz = 1 << v.v_pageshift;
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}
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return(pagesz);
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}
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#endif
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#endif
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